Re: memory leakage in bridge(kernel-2.6.23.14)

From: <redacted>
Date: Wed, 16 Jan 2008 18:04:53 +0800

In SMP, if a bridge fdb is being created when another CPU at the same time
delete the bridge, this newly created fdb may incur a leakage:

netdev@vger.kernel.org (CC:'d) is the proper place to report
things like this.

'linux-net' is only for general user questions about the networking,
not for bug reports, patch postings, or developer discussion.  The
'netdev' list is for that.

Thank you.

CPU0:

static void del_nbp(struct net_bridge_port *p)
{
	/*
	 * CPU1 enter br_fdb_update(), bridge port is still valid.
	 */
	......
	spin_lock_bh(&br->lock);
	br_stp_disable_port(p);
	spin_unlock_bh(&br->lock);

	br_ifinfo_notify(RTM_DELLINK, p);

	br_fdb_delete_by_port(br, p, 1);

	/*
	 * CPU1 call fdb_create() for the being deleted bridge,
	 * a fdb would be add to bridge's fdb hash table, and will never
	 * be freed. because when deleting a bridge, linux flush fdb for
each
	 * bridge port, but this newly created fdb belong to no bridge port
	 */
	......
}

To fix this, fdb_create() should be changed to:
{
	struct net_bridge_fdb_entry *fdb;

	/*
	 * if the bridge port is deleted, then return.
	 */
	if (!(source->state == BR_STATE_LEARNING ||
	      source->state == BR_STATE_FORWARDING))
		return;

	fdb = kmem_cache_alloc(br_fdb_cache, GFP_ATOMIC);
	if (fdb) {
		memcpy(fdb->addr.addr, addr, ETH_ALEN);
		atomic_set(&fdb->use_count, 1);
		hlist_add_head_rcu(&fdb->hlist, head);

		fdb->dst = source;
		fdb->is_local = is_local;
		fdb->is_static = is_local;
		fdb->ageing_timer = jiffies;
	}
	return fdb;
}



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